Farm fields in many areas have rocks mixed with the soil. These rocks interfere with growing plants, damage tillage tools, and damage harvesting machinery. The damage to harvesting machinery can be very expensive and takes substantial periods of time to repair.
Rocks are found in all shapes and sizes. Rocks that are less than about 1.5 inches in diameter cause minimal damage and are generally left in the field. Larger rocks are generally removed periodically.
Freezing and thawing of the ground tends to force rocks to the surface. This results in additional rocks appearing near the surface every year. The quantity of rocks on the surface of the fields varies considerably from one area to another and even from one part of a field to another part of the field.
Mechanical rock pickers have been available for some years. These machines generally handle rocks that are up to about 2 feet in diameter. In areas where the quantity of rocks to be removed is large, rock pickers with a conveyor assembly that continuously moves rocks into a rock hopper are employed. The conveyor assemblies increase the cost of manufacturing as well as the operating costs of these rock pickers. However, continuous conveyors permit these rock pickers to operate continuously until the hopper is full. This continuous operation permits rocks to be picked from a substantial area per hour. In fields where the quantity of rocks to be removed is relatively small, rock pickers are employed that gather rocks in a basket, stop to transfer rocks from the basket to the hopper, and then resume gathering rocks. Elimination of the continuous conveyor reduces manufacturing and operating costs. However, stopping to transfer gathered rocks to the rock hopper takes time and slows the operation. In fields where the quantity of rocks to be removed is low or moderate, rocks can be removed from a substantial area per hour, even though no rocks are removed during the period the machine is stopped to transfer rocks to the rock hopper.
The additional cost of removing rocks with a rock picker with a continuous conveyor is justified only where there is a large quantity of rocks and a large acreage of land to be cleared of rocks.
The rock pickers, that gather the rocks and then stop to transfer the rocks to the rock hopper, tend to drop a few rocks off the tips of the rock gathering tines when the machine is stopped and the gathered rocks are raised and deposited in a hopper on a rock picker. The machine then has to gather these dropped rocks and start with a partially loaded basket assembly when gathering of rocks is resumed.